At present, integrated circuit (IC) chips must be able to allow a wide range of on-chip requirements across devices on the chip to increase circuit performance. However, satisfying the wide range of on-chip requirements across various devices needs to increase the design flexibility, and the process complexity is thus also increased.
For example, gate oxide thickness variation, poly gate length variation, and pocket implantation are usually used to modulate Iddq performance across various devices on a single IC chip. However, as the critical line width of the semiconductor process is continuously decreased, and the operation speed has to be continuously increased, the methods described above are trapped in a bottleneck.
For the method of varying the gate oxide thickness, the material of the gate oxide layer has been replaced by dielectric materials with high dielectric constants, and the thickness of the gate dielectric layer has been greatly decreased to balance the current leakage and the operation speed of a CMOS device. However, the thickness of the gate dielectric layer cannot be decreased anymore, since the thickness of the gate dielectric layer has reached a physical limit. For the method of varying poly gate length, since the variation range of the gate length is majorly limited by the design rule, and the modulation effect is thus limited. For the method of pocket implantation, the current leakage of a CMOS device can be decreased as the doping concentration of the pocket implantation is increased and the doping concentration of source/drain is decreased, but the operation speed of the devices is also sacrificed.